Triterpenoid acids and lactones from the leaves of Fadogia tetraquetra var. tetraquetra (Rubiaceae)

Abstract

Four triterpenoids isolated from the leaves of Fadogia tetraquetra var. tetraquetra, 3β-hydroxy-11α,12α-epoxyoleanan-28,13β-olide (1), 3β-hydroxyurs-11-en-28,13β-olide (2), oleanolic acid (3), and ursolic acid (4), were evaluated for their antiviral and antibacterial properties. Compound 4 showed potent activity against the Semliki Forest virus with an IC50 of 14.7 μM, but was also found to be significantly cytotoxic (68% reduction in cell viability after 24 hours exposure at 50 μM) towards baby hamster kidney (BHK21) host cells. A viability assay on the mammalian human hepatocellular carcinoma (Huh-7) cell line showed no significant effects on intracellular ATP content after 48 hours exposure to compounds 1-4 at this concentration. Compound 4 also inhibited Staphylococcus aureus (MIC 12.5 μM), but was inactive against Enterobacter aerogenes, Escherichia coli, and Pseudomonas aeruginosa. Compounds 1-3 were inactive against all tested bacterial strains at 50 μM concentration.